Magento RMA extension is made for keeping the RMA processes (all the steps of returning a product in order to receive a refund, replacement, or repair during the product's warranty period between the customer and the website owner ) neatly and easier for every website using Magento.

SMS Notification extension for Magento 2 is a comprehensive and powerful module that enables you to send SMSs to your customers or administrators during various events in your Magento store.
Free in integrating custom SMS gateway.